Triton was most likely a captured Dwarf Planet by Neptune. During capture the orbit was very elliptical, thus raising huge tides that heated up the interior (much like Jupiter with Io), initiating massive cryovolcanism that resurfaced Triton. When the orbit settled down, tidal flexing reduced & a new surface froze.

Pluto, as far as is inferred, has never undergone such heating. I think a Triton, Europa, Enceladus, Dione, Ganymede, etc type surface is just wishful thinking. Sure there are ices present & these ices may migrate dependent on the season & the point of the elliptical solar orbit, but Pluto & for that matter the larger & more massive Eris do not appear to have been subjected to violent heating that Triton had.

I think Pluto will look more like Callisto, Rhea or Iapetus. Mostly craters, with perhaps a few fractures. I may be wrong, but that's exploration.

It looks like the Skinakas Basin exists after all, despite being written off, though it is still a bit too soon to jump to that conclusion. The crop & blow up I have just done shows a large feature foreshortened in the northern hemisphere. We will definitely know more tomorrow, as this afternoon's image will be approx 25% closer to Mercury than this one.

There also appears to be another large impact feature in the southern hemisphere. There is clearly a smattering of much smaller craters with bright ejecta blankets in the equatorial region.

Northern horn of crescent Mercury. Looks like there IS a large circular feature foreshortened. I think it is the suspected Skinakas Basin. Obviously we will know much more tomorrow as the second Navigation image will be down, from much closer in.

I suspect Thebe is a rubble pile held together by gravity. The 'pointy' end could be a 'shattercone' where at that end of the original larger object the impact that broke it occurred. With Thebe I have problems with that, i.e the giant crater suggests a rubble pile, not a shattered but hard body.

2867 Šteins, could be a shattercone, possibly once a part of the original larger Asteroid 434 Hungaria (which is now approx 20 KM in diameter).

Enormous deep craters are not that unusual.

Here is a montage I made of the Type C main belt Asteroid 253 Mathilde.

It is known that 253 Mathilde is of very low density, a 'rubble pile' held together, so the porous nature of the asteroid absorbs impacts like punching in polystyrene.

2867 Šteins, I'm not sire. I have not seen any gravity data from Rosetta. The volume of 2867 Šteins is known through the images, so using those together with pertubation data will yield the density. Or was Rosetta passing by too quickly to feel the tug from 2867 Šteins?

Perhaps if the NAC had worked, then greater detail of that 'large' crater on 2867 Šteins, may have helped determine if it's a hole in a rubble pile or was blasted out of more solid, but brittle material.

I assume 2867 Šteins is still thought of being composed of iron poor silicate rich basalt?

243 Ida also has a large crater, but the Galileo data suggested that 243 Ida was too dense to be a rubble pile, but perhaps some parts of the asteroid are not so coherent?

Also Mammoth Crater on main belt Asteroid 243 Ida. Some large boulders are visible.

Did New Horizons image 2 Pallas from afar during the passage of the asteroid belt? Would have been a great test of the LORRI. Or have I misunderstood what you were saying? Most likely.

Hi all,

Had a go at bringing out more detail from the 2 Pallas HST image that Ted posted on the right.

There are definitely some features visible, no doubt.

I hope some image panels of a 2 Pallas rotation will be made up, like those already done for 1 Ceres & 4 Vesta. Also 2 Pallas has some weird seasons, owing to its almost tipped over rotation like Uranus & Asteroid 433 Eros.

The best time to observe the whole of 2 Pallas obviously through a complete rotation would be around the Palladian Equinoxes, though other times would be better for the higher latitudes & polar regions.

Wouldn't that be interesting? We've been seeing that apparently frayed bit of thread in thousands of telltale images for a long time. Still, it would be quite a coincidence.

I wonder if it is a fibre that somehow come off the WindTeller? I think it is. What are the odds of that being a fibre from Mars Pathfinder airbag? Billions to one against, Trillions to one against? Just a thought.

I like that VP, perhaps best not to ask ANY questions that require an intelligent answer on a Sunday.

I have been during quite a bit of gemming up on 2867 Šteins today, but not from Wikipedia.

2867 Šteins although not originally a part of 4 Vesta as per my first theory, does appear to be a chunk knocked off Asteroid 434 Hungaria, so my theory that 2867 Šteins is part of a mantle from a larger body, still stands.

Apparently some Hungaria asteroids do come close to the orbit of Mars, though 2867 Šteins, does not & remains a core member that stays well within the main Asteroid Belt, though E Type main Belt asteroids are incredibly rare, so Rosetta by some very remote & lucky chance encountered one, on only the eigth close asteroid pass (ninth including 243 Ida's moon Dactyl).

I wonder if someone knows. Does 2867 Šteins rotate prograde or retrograde? The Press Conference stated that 2867 Šteins has virtually no axial tilt, but did not mention direction of axial rotation.

My guess is that the sublimation has ceased from Holy Cow & Snow Queen.

I think that you are correct linking the cessation of the growth of the globules on the leg with the lowering Sun.

'Night time' temperatures have lowered on average 5 C / 9 F since the Solstice & that is maybe enough to make the difference. Either way, the end game for Phoenix is drawing closer now but hopefully, she will survive to mid - late November when solar conjunction is nearing & power levels will be desperate.

We are already seeing daily morning H2O frosts now, maybe in the shadows persisting into the afternoons.

AFAIK, the sunlight DID make the regolith clumpiness worse. The idea is that the ice softend in the sun & caused it to stick together. Aslo the scoop is dark, absorbing solar energy, warming it up slightly, thus making the ice rich regolith contained within to clump, as the ice rehardened.

The idea f perhaps scooping some samples in the half light of the polar midnight twilight (as the sun will be setting 'properly' from this Saturday onwards) sounds much better.

Delivering ice rich samples to TEGA should be easier as it should be more of a fine granular mix, rather than the stodgy stuff that has proven so difficult to load.

The minus side of course, with proper night time arriving, well deep twilight (even on Sol 124 the final sol of the current extension, the Sun will only dip to just over four degrees below the horizon at midnight), power will become a big issue.

Will each active period every Sol have to be reduced in duration to allow more time for recharging batteries?

Remember everyone, the solar arrays are dark, so therefore will be warmer than the surface as they absorb more solar energy.Certainly the first frost IS the beginning of the end, averyage Sol temperatures will only get lower now, but I do not think it's signalling the imminent end of the Phoenix Mission & certainly IMO, Sol 124 for the extention mission end is not unreasonable.

What I expect instead, is that surface operations will reduce, as more time will be required to charge the batteries & leep the internal heaters operating.

Perhaps the RA & TEGA will have to be mothballed in the relatively near future, as they do use a lot of power, but the SSI, Meterology suite etc use relatively little & they should operate right to the bitter end.

Interesting observation & certainly now early morning obs should be made compulsory every sol now, to monitor the build up & sublimation of frost.

I was beginning to wonder also. Does anyone know what the resolution of the images at closest approach will be, 1 metre per pixel, better, worse? Hopefully we'll get some more insight as to where Phobos camefrom.

Captured type D asteroid?

Formed around Mars?

Formed from impact ejecta from Mars?

My bet is still option 1, despite the difficulties with explaining orbital mechanics, but I still think, Phobos is as alien to Mars as the spacecraft we have sent.

It will be interesting to compare the new Phobos imagery with the NEAR / Shoemaker spacecraft imagery of similar resolution of asteroid 433 Eros.

Perhaps Mars Express could do similar with Deimos? Comparisons with the MARSIS & multispectral imagers / spectrometers of the two would be most fascinating.

Thanks VP for setting me straight. I was aware of the Janus eclipse, & thought as the original image was so dark, that was taken during said eclipse, not just before.

I see your enhancement, considerably better than mine. I assume the G Ring is responsible for the trapped radiation? I'm not as familiar with the Saturn system as I am of the Jupiter system.

Once again, thanks VP & its great talking to you again.

Hi jasedm, I'm aware of the Enceladus eclipse imagery a while back, faintly lit by Rhea, Dione & Tethys, with Cassini taking a longer exposure, but being further away with a much larger target, it seems to work. Janus is small & close in to Saturn, so yes that would probably not work thinking about it more logically.

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